Flashlamp primer precoating

ABSTRACT

A precoating of rewettable polyvinyl alcohol is provided on the anvil member of a percussion-ignitable flashlamp to improve adherence of the primer coating as well as improve performance of the primer coating when the lamp is actuated.

United States Patent 1 Senft et al.

[54] FLASHLAMP PRIMER PRECOATING 3,521,984 7/1970 Fink et 431/93 9 l 9 71 F' 43l 93 [75] Inventors: Stephen P. Senft, Cleveland Hts.; m

Vaughn C. Sterling, Cleveland, both of Ohio Primary Examiner-Carroll B. Dority, Jr. Assistant ExaminerLarry l. Schwartz Attorney-John F. McDevitt et al.

22] Filed:

Appl. No.: 198,956

[52] US. Cl. 431/93 [51] Int. Fzlk 5/02 A precoating of rewettable polyvinyl alcohol is pro- 431/93, 94;'l49/3, vided on the anvil member of a percussion- Field of Search ignitable flashlamp to improve adherence of the primer coating as well as improve performance of the primer coating when the lamp is actuated.

[56] References Cited UNITED STATES PATENTS 3,137,741 6/1964 Vondersmith et al. 149/11 4 Claims, 2 Drawing Figures PATENTEU DEC 4 73 Fig. 2

Fig,

1 FLASHLAMP PRIMER PRECOATING CROSS-REFERENCES TO RELATED APPLICATIONS The polyvinyl alcohol precoatings of the present invention are especially useful with aqueous primer suspensions and flashlamps described and claimed in concurrently filed U.S. Pat. applications Ser. No. 198,547 now U.S. Pat. No. 3,724,991 and Ser. No. 198,587, now U.S. Pat. No. 3,724,990, both filed in the name of Lewis J. Schupp, and both entitled Photoflash Lamp, which are assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION The hydrophobic nature of the metal anvil employed in percussion-ignitable type flashlamps makes it difficult to gain proper adhesion of the primer coating on the anvil. The aqueous suspensions of primer material described in the above-referenced copending patent applications which include a polyvinyl'alcohol binder were found not to uniformly wet the stainless steel metal used for construction of the anvil and gave rise to flaking or peeling of the solid primer coating during lamp manufacture and lamp use. Additionally, the direct contact between the solid primer coating and anvil metal caused interaction between certain elements in the stainless steel such as iron with constituents in the primer mixture such as phosphorus which subsequently adversely affected reliable ignition of the flashlamp.

SUMMARY OF THE INVENTION It has been discovered, surprisingly, that a precoating of the anvil member in a percussion-ignitable flashlamp with a rewettable type polyvinyl alcohol film provides improved primer adhesion to the anvil and eliminates need for special handling to prevent the mandrel from becoming contaminated with substances such as grease that could reduce the adhesion. Further surprisingly, the introduction of an intervening layer of polyvinyl alcohol between the metal anvil surface and the exterior primer coating has not materially reduced the sensitivity of the primer coating to mechanical impact.

Polyvinyl alcohol precoatings of the present invention can be applied directly to the anvil member of a flashlamp having the configuration described in the above-referenced patent applications. The precoating is generally applied from an aqueous solution of polyvinyl alcohol using conventional application techniques such as dip-forming or spraying and the like. A rewettable grade of partially hydrolyzed polyvinyl alcohol is employed, and it is preferred to use the same hydrolysis grade of polyvinyl alcohol for the precoating as is employed for the binder in the above-referenced improved primer coatings to enhance the cohesion therebetween. in this manner, a film of the rewettable polyvinyl alcohol is first applied to the anvil member and then rewetted with an aqueous suspension of the primer material to form a liquid surface coating of the primer material thereon with final removal of the aqueous liquid providing a unitary mass of the primer material on the anvil member. Medium and high viscosity grades of partially hydrolyzed polyvinyl alcohol having approximately 87-89 percent hydrolysis have been found to provide excellent adhesion of the primer coating on the anvil member in a percussion-ignitable flashlamp.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a percussive type flashlamp construction employing the precoating of the present invention.

FIG. 2 is a perspective view of the anvil member in the FIG. 1 lamp construction which is partly in crosssection to better depict the precoating of the present invention along with a bead of percussively-ignitable primer material adhered to said precoating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a flashlamp employing the present precoating and having a lamp construction as disclosed in the previously referenced copending applications, Ser. Nos. 198,547 and 198,587 comprises a glass bulb or envelope 1 which, as shown may be formed of a short length of glass tubing, for example, about three-eighths inch outside diameter, which is constricted and rounded off at one end as indicated at 2 and closed off thereat by an exhaust tip 3 and is formed at the other or base end 4 with a fused seal 5 about a readily deformable metal ignition tube 6 which may comprise a thin-walled (for example, 0.003-inch wall thickness) tube of a suitable metallic composition such as a nickel-chronium iron alloy, for instance. The envelope 1 is made of a glass which is capable of forming a good hermetic seal to the particular metallic material employed for the ignition tube 6. As shown, the

ignition tube 6 which may have an outside diameter of about one-sixteenth inch, for example, is sealed into the base end 4 of the tubular lamp envelope 1 in a position extending longitudinally and preferably axially thereof, and it projects end-wise from the envelope end 4 to provide an exposed section 7. The ignition tube 6 has a closed outer end 8 and an open inner end 9 which opens into the interior base of the lamp envelope 1 and, as shown, terminates approximately at the inner wall thereof. A quantity of filamentary combustible material 10 such as a shredded foil of zirconium, aluminum or hafnium, for example, is loosely distributed within the interior space of the envelope 1 which also contains a filling of a suitable combustion-supporting gas such as oxygen.

Disposed within the metal ignition tube 6 and extending substantially coaxially therethrough is a wire anvil 1 1 of a suitable metallic composition of high temperature resistance and low thermal condutivity such as, for example, a stainless steel. The wire anvil 11 is suitably held or fastened in place in the ignition tube 6 as by a circumferential indenture 12 of the tube 6 near its outer end which laps over an enlarged head 13 or other suitable protuberance on the outer or lower end of the wire anvil. As shown, the wire anvil 11 is of a slightly smaller diameter than the inside diameter of the ignition tube 6 so as to be spaced a slight distance, for example, about 0.05 inch or so from the inside wall thereof, and it is provided with a thin coating 14 of a pie, 0.004 inch, from the inside wall of the ignition tube.

To aid in supporting the wire anvil 11 substantially axially within the ignition tube 6 and insure clearance between the coating 14 of primer material and the inside wall of the ignition tube 6, the wire anvil 11 is formed near the open inner or mouth end of the ignition tube 6 with two or more protuberances or lobes spaced apart more or less uniformly around the circumferential extent of the wire anvil and having, along the head 13 on the wire anvil, a close sliding fit within the ignition tube. The anvil centralizing lobes 15 are of minimal thickness circumferentially of the wire anvil 11 so as to leave substantially unobstructed the annular space between the ignition tube 6 and the wire anvil 1 1 for the passage therethrough and into the lamp envelope 1 of the ignited particles of the primer material 14 upon ignition and deflagration thereof. In the particular case illustrated, the anvil centralizing lobes 15 are formed by flattening the wire anvil 11 at two closely adjacent points around the length of the anvil and into different planes at approximately the right angles to one another. The lamp is also provided with a deflector shield 16 which is located just inwardly of the open inner mouth end 9 of the ignition tube 6 on an inwardly extending portion 17 of the wire anvil 11 that extends into the lamp envelope 1 from the mouth opening 9 of the ignition tube 6. The deflector shield 16 can be constituted by a glass bead fusion-sealed to the wire anvil 11.

An alternate form'of the anvil member has the deflector shield 16 being constituted by an upset or extruded integral concentric collar or flange portion 18 of the wire anvil being formed of the same metallic material as the anvil itself. For either type anvil construction, the anvil member can be entirely coated with a precoating of the present rewettable polyvinyl alcohol material as shown more clearly in FIG. 2. More particularly, the anvils can be immersed after cleaning in a liquid coating composition of said precoating material and thereafter removed from the liquid coating composition to allow excess coating to drain off, after which the precoated anvils are allowed to dry and can be stored prior to application of the primer material thereon. As shown in FIG. 2, the precoating 19 underlies the bead of primer material 14 which is subsequently applied over an appreciably lengthwise entent of that portion of the wire anvil located within the projecting portion 7 of the ignition tube 6.

By way of specific example, cleaned anvils can be immersed in an aqueous polyvinyl alcohol solution having a weight range of 1-3% polyvinyl alcohol after surface grease and other contaminants have been removed from the exterior surface of the anvil members. Excess solution is permitted to drain off the anvils after which the precoating is dried in ordinary air or with heat to provide a precoating which thereafter permits ordinary handling of the precoated anvils prior and during application of the primer coating.

An aqueous solution of polyvinyl alcohol which is useful for the precoating can be prepared from a medium or high viscosity grade of the commercial solid polymer, preferably having the degree of hydrolysis hereinbefore specified, by mixing in water with agitation. Vigorous mixing and warm water speeds the solution process at the low weight percentages of polymer which can be used to provide satisfactory films on the mandrel. While such aqueous solutions of polyvinyl alcohol have proven quite stable and did not gel in storage, it may become advisable to employ a small amount of mold inhibitor or other additives in the solution if storage over long time periods is being contemplated. The addition of conventional amounts of mold inhibitor or other compatible additives has not been found to adversely affect the desired performance of the polyvinyl alcohol film, but it has not been found necessary to employ plasticizers in the film to avoid brittleness.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a percussion-ignitable flashlamp, an anvil member coated with a rewettable polyvinyl alcohol film having adhered thereto as a surface layer a unitary mass of a primer material bonded with a polyvinyl alcohol binder.

2. A coated anvil member as in claim 1 wherein the polyvinyl alcohol film is approximately 87-89% hydrolyzed polyvinyl alcohol.

3. A coated anvil member as in claim 1 wherein the polyvinyl alcohol film and polyvinyl alcohol binder are both approximately 87-89% hydrolyzed polyvinyl alcohol.

4. A method of coating the anvil member of a percussion-ignitable flashlamp which comprises:

a. applying a film of a rewettable polyvinyl alcohol t i said anvil member,

b. rewetting said polyvinyl alcohol film with an aqueous suspension of a primer material in a polyvinyl alcohol binder to form a liquid surface coating of the primer material thereon, and

c. removing the aqueous liquid to form a unitary mass of the primer material on the anvil member. 

2. A coated anvil member as in claim 1 wherein the polyvinyl alcohol film is approximately 87-89% hydrolyzed polyvinyl alcohol.
 3. A coated anvil member as in claim 1 wherein the polyvinyl alcohol film and polyvinyl alcohol binder are both approximately 87-89% hydrolyzed polyvinyl alcohol.
 4. A method of coating the anvil member of a percussion-ignitable flashlamp which comprises: a. applying a film of a rewettable polyvinyl alcohol to said anvil member, b. rewetting said polyvinyl alcohol film with an aqueous suspension of a primer material in a polyvinyl alcohol binder to form a liquid surface coating of the primer material thereon, and c. removing the aqueous liquid to form a unitary mass of the primer material on the anvil member. 